Conventionally, cable television systems transmit audio and video signals for a number of different channels to subscribers from a head end over a network. The cable television system receives audio and video feeds from content providers. Such content providers typically include a number of local channels, e.g, local network affiliates, community access channels, as well as a number of national and premium channels, e.g., Cable Network News (CNN), Entertainment and Sports Programming Network (ESPN), TNT, USA Network, Home Box Office (HBO), Nickelodian. Typically, a cable television system contracts with the content providers for the option to transmit local commercial advertisements on many of these national and premium channels. At the same time that such local advertisements are running, the content providers also transmit national advertisements in their audio/video feed to be broadcast over local systems that do not exercise the option to air local commercials. Thus, the local cable television system typically has equipment that allows the local advertisements to be inserted in place of the national advertisements.
Conventionally, a cable network receives audio and video signals (the "feed") from the content providers at a central site commonly referred to as the "head end" or the "central" or "main" head end. These signals are then transmitted over, for example, a fiber optic transport ring to a number of geographically dispersed sites referred to as "remote" head ends. The signals from the remote head ends are then provided over, for example, coaxial cable to subscriber equipment, e.g., a television in a residence or business.
To allow for insertion of local advertisements, conventional cable systems typically use a server at each remote head end that stores the advertisements in a compressed format, e.g., formats specified by the Motion Pictures Expert Group, known collectively as "MPEG" standards, for broadcast over the cable network when scheduled. Such servers are commercially available from Sea Change International of Maynard, Mass. These servers are expensive to install and contribute a significant cost to the cable television system. Further, the servers are expensive to maintain. Typically, the servers are maintained by a trained technician at each site or an individual who travels between the remote head ends. In either event, the costs associated with operating the server that inserts the local advertisements is significant.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a more economical system and method for allowing local modification of an information signal.